Methods of ul tdm for inter-enodeb carrier aggregation

ABSTRACT

One or more embodiments provide a method implemented in a user equipment (UE) used in a wireless communications system. The method includes transmitting an indication to a base station that the UE is capable of transmitting on a single uplink carrier frequency and downlink carrier aggregation. The method also includes receiving an uplink carrier frequency switching pattern from the base station. The method also includes switching uplink carrier frequencies based on the uplink carrier frequency switching pattern.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/583,560, filed May 1, 2017, which is a continuation of U.S. patentapplication Ser. No. 14/304,459, filed Jun. 13, 2014, now U.S. Pat. No.9,642,140, which claims priority to U.S. Provisional Patent ApplicationNo. 61/836,532, filed Jun. 18, 2013, and U.S. Provisional PatentApplication No. 61/858,018, filed Jul. 24, 2013, the disclosures ofwhich are herein incorporated by reference in their entirety.

TECHNICAL FIELD

The present application relates generally to wireless communicationsystems and, more specifically, to uplink carrier switching forinter-eNodeB or inter-site carrier aggregation.

BACKGROUND

In Rel-10 LTE, the UE can be configured with multiple downlink carrierfrequencies for downlink carrier aggregation and only one uplink carrierfrequency. The primary component carrier comprises of a pair of downlinkand uplink carriers (on different frequencies for FDD system and on thesame frequency for TDD system), while the secondary component carriermay comprise only a single downlink carrier frequency with no uplinkcarrier frequency. Layer 1 uplink control information associated withthe secondary component carrier is always transmitted on the primarycomponent carrier.

There is benefit to enable aggregation of two or more downlink carrierfrequencies for a UE where different carrier frequency is associatedwith different eNodeB and the eNodeBs concerned may not be co-located atthe same site (inter-site inter-eNodeB carrier aggregation). This isalso known as non-co-channel dual connectivity. A certain deploymentscenario may have different neighboring eNodeB configured with differentdownlink and uplink carrier pair. A certain deployment scenario may alsohave the eNodeBs interconnected with slow backhaul (e.g. 40 ms on-waytransmission latency).

When inter-eNodeB carrier aggregation is configured, the traffic to theUE may predominantly flow through a particular carrier. In one example,traffic with best effort QoS may predominantly flow through one carrierwhile traffic with stricter QoS may predominantly flow through anothercarrier. In another example, traffic may predominantly flow through onecarrier because the corresponding path loss may be lower.

When the UE is configured with carrier aggregation where a first eNodeBis associated with the primary component carrier and a second eNodeB isassociated with the secondary component carrier, it is not desirable forthe UE to transmit Layer 1 uplink control information corresponding tothe second component carrier to the primary component carrier due to theexcessive latency incurred for the first eNodeB to transmit the Layer 1uplink control information corresponding to the second component carrierto the second eNodeB over the X2 interface. Therefore, there is a needto transmit uplink control information and uplink data associated withan eNodeB directly over the air to the eNodeB concerned when inter-siteinter-eNodeB carrier aggregation is configured.

SUMMARY

An embodiment provides a method implemented in a user equipment (UE)used in a wireless communications system. The method includestransmitting an indication to a base station that the UE is capable oftransmitting on a single uplink carrier frequency and downlink carrieraggregation. The method also includes receiving an uplink carrierfrequency switching pattern from the base station. The method alsoincludes switching uplink carrier frequencies based on the uplinkcarrier frequency switching pattern.

An embodiment provides a method implemented in a base station used in awireless communications system. The method includes receiving anindication that user equipment (UE) is capable of transmitting on asingle uplink carrier frequency and downlink carrier aggregation. Themethod also includes transmitting an uplink carrier frequency switchingpattern from the base station. The UE switches uplink carrierfrequencies based on the uplink carrier frequency switching pattern.

An embodiment provides a user equipment (UE) used in a wirelesscommunications system. The UE includes a transceiver and a controller.The transceiver is configured to transmit an indication to a basestation that the UE is capable of transmitting on a single uplinkcarrier frequency and downlink carrier aggregation and receive an uplinkcarrier frequency switching pattern from the base station. Thecontroller is configured to switch uplink carrier frequencies based onthe uplink carrier frequency switching pattern.

An embodiment provides a base station used in a wireless communicationssystem. The base station includes a transceiver. The transceiver isconfigured to receive an indication that user equipment (UE) is capableof transmitting on a single uplink carrier frequency and downlinkcarrier aggregation and transmit an uplink carrier frequency switchingpattern from the base station. The UE switches uplink carrierfrequencies based on the uplink carrier frequency switching pattern.

Before undertaking the DETAILED DESCRIPTION below, it may beadvantageous to set forth definitions of certain words and phrases usedthroughout this patent document: the terms “include” and “comprise,” aswell as derivatives thereof, mean inclusion without limitation; the term“or,” is inclusive, meaning and/or; the phrases “associated with” and“associated therewith,” as well as derivatives thereof, may mean toinclude, be included within, interconnect with, contain, be containedwithin, connect to or with, couple to or with, be communicable with,cooperate with, interleave, juxtapose, be proximate to, be bound to orwith, have, have a property of, or the like; and the term “controller”means any device, system or part thereof that controls at least oneoperation, such a device may be implemented in hardware, firmware orsoftware, or some combination of at least two of the same. It should benoted that the functionality associated with any particular controllermay be centralized or distributed, whether locally or remotely.Definitions for certain words and phrases are provided throughout thispatent document, those of ordinary skill in the art should understandthat in many, if not most instances, such definitions apply to prior, aswell as future uses of such defined words and phrases.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present disclosure and itsadvantages, reference is now made to the following description taken inconjunction with the accompanying drawings, in which like referencenumerals represent like parts:

FIG. 1 illustrates an example wireless network according to thisdisclosure;

FIG. 2 illustrates an example eNodeB (eNB) according to this disclosure;

FIG. 3 illustrates an example user equipment (UE) according to thisdisclosure;

FIG. 4 illustrates a structure of a DL Transmission Time Interval (TTI)according to this disclosure;

FIG. 5 illustrates a structure of a UL TTI for a PUSCH transmissionaccording to this disclosure;

FIG. 6 illustrates a structure for a first PUCCH format for transmittinga HARQ-ACK signal in a TTI according to this disclosure;

FIG. 7 illustrates a structure for a second PUCCH format fortransmitting a HARQ-ACK signal in a TTI according to this disclosure;

FIG. 8 illustrates an example of physical uplink shared channel (PUSCH)resource allocation according to this disclosure;

FIG. 9 illustrates an example uplink carrier frequency switching patternaccording to this disclosure;

FIG. 10 illustrates an example process for determining which uplinkcarrier frequency for transmission according to this disclosure;

FIG. 11 illustrates an example uplink carrier frequency switchingpattern according to this disclosure;

FIG. 12 illustrates an example of configurable switching period patternsaccording to this disclosure;

FIGS. 13A-13B illustrate example of PDCCH/EPDCCH monitoring behaviorsaccording to this disclosure;

FIGS. 14A-14B illustrate example of PUSCH in subframes according to thisdisclosure;

FIG. 15 illustrates an example process for determining an uplink TTIswitching pattern for FDD and TDD joint operation according to thisdisclosure;

FIG. 16 illustrates an example process for determining the number ofbits for a DL HARQ process index field of an FDD cell according to thisdisclosure;

FIG. 17 illustrates an example process for determining an existence of aDL DAI field in a DL DCI format depending on whether a primary cell isan FDD cell or a TDD cell according to this disclosure; and

FIG. 18 illustrates an example process for determining an existence ofan UL DAI field in a DL DCI format depending on whether a FDD UL-DLconfiguration is enabled or not according to this disclosure.

DETAILED DESCRIPTION

FIGS. 1 through 18, discussed below, and the various embodiments used todescribe the principles of the present invention in this patent documentare by way of illustration only and should not be construed in any wayto limit the scope of the disclosure. Those skilled in the art willunderstand that the principles of this disclosure may be implemented inany suitably arranged device or system.

FIG. 1 illustrates an example wireless network 100 according to thisdisclosure. The embodiment of the wireless network 100 shown in FIG. 1is for illustration only. Other embodiments of the wireless network 100could be used without departing from the scope of this disclosure.

As shown in FIG. 1, the wireless network 100 includes an eNodeB (eNB)101, an eNB 102, and an eNB 103. The eNB 101 communicates with the eNB102 and the eNB 103. The eNB 101 also communicates with at least oneInternet Protocol (IP) network 130, such as the Internet, a proprietaryIP network, or other data network.

The eNB 102 provides wireless broadband access to the network 130 for afirst plurality of user equipments (UEs) within a coverage area 120 ofthe eNB 102. The first plurality of UEs includes a UE 111, which may belocated in a small business (SB); a UE 112, which may be located in anenterprise (E); a UE 113, which may be located in a Wi-Fi hotspot (HS);a UE 114, which may be located in a first residence (R); a UE 115, whichmay be located in a second residence (R); and a UE 116, which may be amobile device (M) like a cell phone, a wireless laptop, a wireless PDA,or the like. The eNB 103 provides wireless broadband access to thenetwork 130 for a second plurality of UEs within a coverage area 125 ofthe eNB 103. The second plurality of UEs includes the UE 115 and the UE116. In some embodiments, one or more of the eNBs 101-103 maycommunicate with each other and with the UEs 111-116 using 5G, LTE,LTE-A, WiMAX, Wi-Fi, or other wireless communication techniques.

Depending on the network type, other well-known terms may be usedinstead of “eNodeB” or “eNB,” such as “base station” or “access point.”For the sake of convenience, the terms “eNodeB” and “eNB” are used inthis patent document to refer to network infrastructure components thatprovide wireless access to remote terminals. Also, depending on thenetwork type, other well-known terms may be used instead of “userequipment” or “UE,” such as “mobile station,” “subscriber station,”“remote terminal,” “wireless terminal,” or “user device.” For the sakeof convenience, the terms “user equipment” and “UE” are used in thispatent document to refer to remote wireless equipment that wirelesslyaccesses an eNB, whether the UE is a mobile device (such as a mobiletelephone or smartphone) or is normally considered a stationary device(such as a desktop computer or vending machine).

Dotted lines show the approximate extents of the coverage areas 120 and125, which are shown as approximately circular for the purposes ofillustration and explanation only. It should be clearly understood thatthe coverage areas associated with eNBs, such as the coverage areas 120and 125, may have other shapes, including irregular shapes, dependingupon the configuration of the eNBs and variations in the radioenvironment associated with natural and man-made obstructions.

As described in more detail below, an embodiment provides a methodimplemented in a base station used in a wireless communications system.The method includes receiving an indication that user equipment (UE) iscapable of transmitting on a single uplink carrier frequency anddownlink carrier aggregation. The method also includes transmitting anuplink carrier frequency switching pattern from the base station. The UEswitches uplink carrier frequencies based on the uplink carrierfrequency switching pattern.

Although FIG. 1 illustrates one example of a wireless network 100,various changes may be made to FIG. 1. For example, the wireless network100 could include any number of eNBs and any number of UEs in anysuitable arrangement. Also, the eNB 101 could communicate directly withany number of UEs and provide those UEs with wireless broadband accessto the network 130. Similarly, each eNB 102-103 could communicatedirectly with the network 130 and provide UEs with direct wirelessbroadband access to the network 130. Further, the eNB 101, 102, and/or103 could provide access to other or additional external networks, suchas external telephone networks or other types of data networks.

FIG. 2 illustrates an example eNB 102 according to this disclosure. Theembodiment of the eNB 102 illustrated in FIG. 2 is for illustrationonly, and the eNBs 101 and 103 of FIG. 1 could have the same or similarconfiguration. However, eNBs come in a wide variety of configurations,and FIG. 2 does not limit the scope of this disclosure to any particularimplementation of an eNB.

As shown in FIG. 2, the eNB 102 includes multiple antennas 205 a-205 n,multiple RF transceivers 210 a-210 n, transmit (TX) processing circuitry215, and receive (RX) processing circuitry 220. The eNB 102 alsoincludes a controller/processor 225, a memory 230, and a backhaul ornetwork interface 235.

The RF transceivers 210 a-210 n receive, from the antennas 205 a-205 n,incoming RF signals, such as signals transmitted by UEs in the network100. The RF transceivers 210 a-210 n down-convert the incoming RFsignals to generate IF or baseband signals. The IF or baseband signalsare sent to the RX processing circuitry 220, which generates processedbaseband signals by filtering, decoding, and/or digitizing the basebandor IF signals. The RX processing circuitry 220 transmits the processedbaseband signals to the controller/processor 225 for further processing.

The TX processing circuitry 215 receives analog or digital data (such asvoice data, web data, e-mail, or interactive video game data) from thecontroller/processor 225. The TX processing circuitry 215 encodes,multiplexes, and/or digitizes the outgoing baseband data to generateprocessed baseband or IF signals. The RF transceivers 210 a-210 nreceive the outgoing processed baseband or IF signals from the TXprocessing circuitry 215 and up-converts the baseband or IF signals toRF signals that are transmitted via the antennas 205 a-205 n.

The controller/processor 225 can include one or more processors or otherprocessing devices that control the overall operation of the eNB 102.For example, the controller/processor 225 could control the reception offorward channel signals and the transmission of reverse channel signalsby the RF transceivers 210 a-210 n, the RX processing circuitry 220, andthe TX processing circuitry 215 in accordance with well-knownprinciples. The controller/processor 225 could support additionalfunctions as well, such as more advanced wireless communicationfunctions. For instance, the controller/processor 225 could support beamforming or directional routing operations in which outgoing signals frommultiple antennas 205 a-205 n are weighted differently to effectivelysteer the outgoing signals in a desired direction. Any of a wide varietyof other functions could be supported in the eNB 102 by thecontroller/processor 225. In some embodiments, the controller/processor225 includes at least one microprocessor or microcontroller.

The controller/processor 225 is also capable of executing programs andother processes resident in the memory 230, such as a basic OS. Thecontroller/processor 225 can move data into or out of the memory 230 asrequired by an executing process.

The controller/processor 225 is also coupled to the backhaul or networkinterface 235. The backhaul or network interface 235 allows the eNB 102to communicate with other devices or systems over a backhaul connectionor over a network. The interface 235 could support communications overany suitable wired or wireless connection(s). For example, when the eNB102 is implemented as part of a cellular communication system (such asone supporting 5G, LTE, or LTE-A), the interface 235 could allow the eNB102 to communicate with other eNBs over a wired or wireless backhaulconnection. When the eNB 102 is implemented as an access point, theinterface 235 could allow the eNB 102 to communicate over a wired orwireless local area network or over a wired or wireless connection to alarger network (such as the Internet). The interface 235 includes anysuitable structure supporting communications over a wired or wirelessconnection, such as an Ethernet or RF transceiver.

The memory 230 is coupled to the controller/processor 225. Part of thememory 230 could include a RAM, and another part of the memory 230 couldinclude a Flash memory or other ROM.

Although FIG. 2 illustrates one example of eNB 102, various changes maybe made to FIG. 2. For example, the eNB 102 could include any number ofeach component shown in FIG. 2. As a particular example, an access pointcould include a number of interfaces 235, and the controller/processor225 could support routing functions to route data between differentnetwork addresses. As another particular example, while shown asincluding a single instance of TX processing circuitry 215 and a singleinstance of RX processing circuitry 220, the eNB 102 could includemultiple instances of each (such as one per RF transceiver). Also,various components in FIG. 2 could be combined, further subdivided, oromitted and additional components could be added according to particularneeds.

FIG. 3 illustrates an example UE 116 according to this disclosure. Theembodiment of the UE 116 illustrated in FIG. 3 is for illustration only,and the UEs 111-115 of FIG. 1 could have the same or similarconfiguration. However, UEs come in a wide variety of configurations,and FIG. 3 does not limit the scope of this disclosure to any particularimplementation of a UE.

As shown in FIG. 3, the UE 116 includes an antenna 305, a radiofrequency (RF) transceiver 310, transmit (TX) processing circuitry 315,a microphone 320, and receive (RX) processing circuitry 325. The UE 116also includes a speaker 330, a main processor 340, an input/output (I/O)interface (IF) 345, a keypad 350, a display 355, and a memory 360. Thememory 360 includes a basic operating system (OS) program 361 and one ormore applications 362.

The RF transceiver 310 receives, from the antenna 305, an incoming RFsignal transmitted by an eNB of the network 100. The RF transceiver 310down-converts the incoming RF signal to generate an intermediatefrequency (IF) or baseband signal. The IF or baseband signal is sent tothe RX processing circuitry 325, which generates a processed basebandsignal by filtering, decoding, and/or digitizing the baseband or IFsignal. The RX processing circuitry 325 transmits the processed basebandsignal to the speaker 330 (such as for voice data) or to the mainprocessor 340 for further processing (such as for web browsing data).

The TX processing circuitry 315 receives analog or digital voice datafrom the microphone 320 or other outgoing baseband data (such as webdata, e-mail, or interactive video game data) from the main processor340. The TX processing circuitry 315 encodes, multiplexes, and/ordigitizes the outgoing baseband data to generate a processed baseband orIF signal. The RF transceiver 310 receives the outgoing processedbaseband or IF signal from the TX processing circuitry 315 andup-converts the baseband or IF signal to an RF signal that istransmitted via the antenna 305.

The main processor 340 can include one or more processors or otherprocessing devices and execute the basic OS program 361 stored in thememory 360 in order to control the overall operation of the UE 116. Forexample, the main processor 340 could control the reception of forwardchannel signals and the transmission of reverse channel signals by theRF transceiver 310, the RX processing circuitry 325, and the TXprocessing circuitry 315 in accordance with well-known principles. Insome embodiments, the main processor 340 includes at least onemicroprocessor or microcontroller.

The main processor 340 is also capable of executing other processes andprograms resident in the memory 360. The main processor 340 can movedata into or out of the memory 360 as required by an executing process.In some embodiments, the main processor 340 is configured to execute theapplications 362 based on the OS program 361 or in response to signalsreceived from eNBs or an operator. The main processor 340 is alsocoupled to the I/O interface 345, which provides the UE 116 with theability to connect to other devices such as laptop computers andhandheld computers. The I/O interface 345 is the communication pathbetween these accessories and the main processor 340.

The main processor 340 is also coupled to the keypad 350 and the displayunit 355. The operator of the UE 116 can use the keypad 350 to enterdata into the UE 116. The display 355 may be a liquid crystal display orother display capable of rendering text and/or at least limitedgraphics, such as from web sites.

The memory 360 is coupled to the main processor 340. Part of the memory360 could include a random access memory (RAM), and another part of thememory 360 could include a Flash memory or other read-only memory (ROM).

Although FIG. 3 illustrates one example of UE 116, various changes maybe made to FIG. 3. For example, various components in FIG. 3 could becombined, further subdivided, or omitted and additional components couldbe added according to particular needs. As a particular example, themain processor 340 could be divided into multiple processors, such asone or more central processing units (CPUs) and one or more graphicsprocessing units (GPUs). Also, while FIG. 3 illustrates the UE 116configured as a mobile telephone or smartphone, UEs could be configuredto operate as other types of mobile or stationary devices.

One or more embodiments of the disclosure relate to wirelesscommunication systems and, more specifically, to an aggregation of acarrier using Frequency Division Duplexing (FDD) and of a carrier usingTime Division Duplexing (TDD). A communication system includes aDownLink (DL) that conveys signals from transmission points such as BaseStations (BSs) or NodeBs to User Equipments (UEs) and an UpLink (UL)that conveys signals from UEs to reception points such as NodeBs. A UE,also commonly referred to as a terminal or a mobile station, may befixed or mobile and may be a cellular phone, a personal computer device,etc. A NodeB, which is generally a fixed station, may also be referredto as an access point or other equivalent terminology.

DL signals include data signals conveying information content, controlsignals conveying DL Control Information (DCI), and Reference Signals(RS), which are also known as pilot signals. A NodeB transmits datainformation or DCI through respective Physical DL Shared CHannels(PDSCHs) or Physical DL Control CHannels (PDCCHs). A NodeB transmits oneor more of multiple types of RS including a UE-Common RS (CRS), aChannel State Information RS (CSI-RS), and a DeModulation RS (DMRS). ACRS is transmitted over a DL system BandWidth (BW) and can be used byUEs to demodulate data or control signals or to perform measurements. Toreduce CRS overhead, a NodeB may transmit a CSI-RS with a smallerdensity in the time and/or frequency domain than a CRS. For channelmeasurement, Non-Zero Power CSI-RS (NZP CSI-RS) resources can be used.For Interference Measurement Reports (IMRs), CSI InterferenceMeasurement (CSI-IM) resources associated with a Zero Power CSI-RS (ZPCSI-RS) can be used. A UE can determine the CSI-RS transmissionparameters through higher layer signaling from a NodeB. DMRS istransmitted only in the BW of a respective PDSCH and a UE can use theDMRS to demodulate information in a PDSCH.

FIG. 4 illustrates a structure of a DL Transmission Time Interval (TTI)400 according to this disclosure. The embodiment of the TTI 400illustrated in FIG. 4 is for illustration only, and the UEs 111-115 ofFIG. 1 could have the same or similar configuration. However, UEs comein a wide variety of configurations, and FIG. 4 does not limit the scopeof this disclosure to any particular implementation of a UE.

As shown in FIG. 4, the TTI 400 includes OFDM symbols 402, OFDM symbols404, and OFDM symbols 406. In one embodiment, the UE can be configuredwith TTI 400 and the UE could retune its uplink carrier frequency inaccordance with the TTI 400.

Referring to FIG. 4, DL signaling uses Orthogonal Frequency DivisionMultiplexing (OFDM) and a DL TTI includes N=14 OFDM symbols in the timedomain and K Resource Blocks (RBs) in the frequency domain. A first typeof Control CHannels (CCHs) is transmitted in a first N1 OFDM symbols 402(including no transmission, N₁=0). A remaining N-N₁OFDM symbols 404 areused primarily for transmitting PDSCHs and, in some RBs of a TTI, fortransmitting a second type of CCHs (ECCHs) 406.

UL signals also include data signals conveying information content,control signals conveying UL Control Information (UCI), and RS. A UEtransmits data information or UCI through a respective Physical ULShared CHannel (PUSCH) or a Physical UL Control CHannel (PUCCH). If a UEsimultaneously transmits data information and UCI, it may multiplex bothin a PUSCH. UCI includes Hybrid Automatic Repeat reQuest ACKnowledgement(HARQ-ACK) information, indicating correct or incorrect detection ofdata Transport Blocks (TBs) in a PDSCH, Service Request (SR) indicatingwhether a UE has data in its buffer, and Channel State Information (CSI)enabling a NodeB to select appropriate parameters for PDSCH or PDCCHtransmissions to a UE. UL RS includes DMRS and Sounding RS (SRS). DMRSis transmitted only in a BW of a respective PUSCH or PUCCH and primarilyserves to enable coherent demodulation of information in a PUSCH orPUCCH at a NodeB. SRS is transmitted by a UE to provide a NodeB with anUL CSI. For initial access or for subsequent synchronization purposes, aUE can also be configured by a NodeB to transmit a Random Access CHannel(RACH).

FIG. 5 illustrates a structure 500 of a UL TTI 502 for a PUSCHtransmission according to this disclosure. The embodiment of thestructure 500 illustrated in FIG. 5 is for illustration only, and theUEs 111-115 of FIG. 1 could have the same or similar configuration.However, UEs come in a wide variety of configurations, and FIG. 5 doesnot limit the scope of this disclosure to any particular implementationof a UE.

As shown in FIG. 5, the structure 500 includes uplink TTI 502, slot 504,symbol 506, DMRS slot 508, resource block 510, and symbol 512. In oneembodiment, the UE can be configured with structure 500 and the UE couldretune its uplink carrier frequency in accordance with the structure500.

Referring to FIG. 5, UL signaling uses Discrete Fourier Transform SpreadOFDM (DFT-S-OFDM) and an UL TTI 502 includes two slots. Each slot 504includes N_(symb) ^(UL) symbols 506 for transmitting data information,UCI, or RS. Some PUSCH symbols in each slot are used for transmittingDMRS 508. A transmission BW includes RBs with each RB including N_(sc)^(RB) sub-carriers, or Resource Elements (REs). A UE is allocatedM_(PUSCH) RBs 510 for a total of M_(sc) ^(PUSCH)=M_(PUSCH)·M_(sc)^(RB)REs for a PUSCH transmission BW. The last TTI symbol may be used tomultiplex SRS transmissions 512 from one or more UEs. A number of TTIsymbols available for data/UCI/DMRS transmission is N_(symb)^(PUSCH)=2·(N_(symb) ^(UL)−1)−N_(SRS), where N_(SRS)=1 if a TTI supportsSRS transmissions and a PUSCH transmission BW at least partially overlapwith a SRS transmission BW and N_(SRS)=0 otherwise.

FIG. 6 illustrates a structure 600 for a first PUCCH format fortransmitting a HARQ-ACK signal in a TTI according to this disclosure.The embodiment of the structure 600 illustrated in FIG. 6 is forillustration only, and the UEs 111-115 of FIG. 1 could have the same orsimilar configuration. However, UEs come in a wide variety ofconfigurations, and FIG. 6 does not limit the scope of this disclosureto any particular implementation of a UE.

As shown in FIG. 6, the structure 600 includes slot 602, symbols604-606, HARQ-ACK bits b 608, modulate 610, Zadoff-Chu sequence 612, andtransmission 614. In one embodiment, the UE can be configured withstructure 600 and the UE could retune its uplink carrier frequency inaccordance with the structure 600.

Referring to FIG. 6, a TTI includes two slots and each slot 602 includesN_(symb) ^(UL) symbols 604-606 for transmitting HARQ-ACK signals (symbol604) or RS (symbol 606) in a RB. HARQ-ACK bits 608 modulate 610 aZadoff-Chu (ZC) sequence 612 of length N_(sc) ^(RB) using Binary PhaseShift Keying (BPSK) or Quaternary Phase Shift Keying (QPSK) modulation.A HARQ-ACK bit can have a numeric value of −1 if it conveys a positiveACKnowledgement (ACK) for a correct detection of a data TB and a numericvalue of 1 if it conveys a Negative ACKnowledgement (NACK) for a correctdetection of a data TB. In general, absence of a data TB reception isreferred to as DTX and can have a same representation as a NACK. Amodulated ZC sequence is transmitted 614 after performing an InverseFast Frequency Transform (IFFT). A RS is transmitted through anunmodulated ZC sequence.

A first PUCCH format with structure as in FIG. 6 is capable ofsupporting transmission of only one or two HARQ-ACK bits. When multiplePUCCH resources exist for a UE to select for HARQ-ACK signaltransmission, a combination of PUCCH resource selection and a use of afirst PUCCH format as in FIG. 6, referred to as PUCCH format 1b, cansupport transmissions of up to four HARQ-ACK bits. A second PUCCHformat, referred to as PUCCH format 3, can also be used to transmit alarge number of HARQ-ACK bits such as, for example, up to 22 bits.

FIG. 7 illustrates a structure 700 for a second PUCCH format fortransmitting a HARQ-ACK signal in a TTI according to this disclosure.The embodiment of the structure 700 illustrated in FIG. 7 is forillustration only, and the UEs 111-115 of FIG. 1 could have the same orsimilar configuration. However, UEs come in a wide variety ofconfigurations, and FIG. 7 does not limit the scope of this disclosureto any particular implementation of a UE.

As shown in FIG. 7, the structure 700 includes slot 702, HARQ-ACK bits704, Orthogonal Covering Code (OCC) 706, multiplier 708, DFT precoder710, IFFT 712, symbol 714, sequence 716, IFFT 718, and symbol 720. Inone embodiment, the UE can be configured with structure 700 and the UEcould retune its uplink carrier frequency in accordance with thestructure 700.

Referring to FIG. 7, a TTI includes two slots and each slot 702 includessymbols for transmitting HARQ-ACK signals or RS in a RB. HARQ-ACK signaltransmission uses DFT-S-OFDM. After encoding and modulation, usingrespectively a block code such as a Reed-Muller (RM) code and QuaternaryPhase Shift Keying (QPSK), respectively, a set of same HARQ-ACK bits 704is multiplied by multiplier 708 with elements of an Orthogonal CoveringCode (OCC) 706 and is subsequently DFT precoded by DFT precoder 710. Forexample, for five DFT-S-OFDM symbols per slot for HARQ-ACK signaltransmission, an OCC of length five is used. An output is passed throughan IFFT 712 and it is then mapped to a DFT-S-OFDM symbol 714. As theoperations are linear, their relative order may be inter-changed. Sameor different HARQ-ACK bits may be transmitted in a second slot of a TTI.RS is also transmitted in each slot to enable coherent demodulation ofHARQ-ACK signals. A RS is constructed from a ZC sequence 716 of lengthN_(sc) ^(RB) which is passed through an IFFT 718 and mapped to anotherDFT-S-OFDM symbol 720.

If a UE detects for a cell c a DL DCI format scheduling a PDSCHreception with one data TB or with two data TBs and the UE appliesbundling (using an XOR operation) between two HARQ-ACK information bitsgenerated in response to a reception of the two data TBs (spatial-domainbundling), the UE generates o_(c)=1 HARQ-ACK information bit (in caseone data TB is conveyed when a configured transmission mode is for twodata TBs, an ACK is assumed for the not transmitted data TB); otherwise,the UE generates o_(c)=2 HARQ-ACK information bits.

A PDSCH transmission to a UE or a PUSCH transmission from a UE can beeither dynamically scheduled or Semi-Persistently Scheduled (SPS).Dynamic transmissions are triggered by a DCI format that is conveyed bya PDCCH and includes fields providing PDSCH or PUSCH transmissionparameters while SPS transmission parameters are configured to a UE froma NodeB through higher layer signaling such as Radio Resource Control(RRC) signaling. A DCI format scheduling a PDSCH transmission isreferred to as DL DCI format while a DCI format scheduling a PUSCHtransmission is referred to as UL DCI format.

In a TDD communication system, the communication direction in some TTIsis in the DL and in some other TTIs is in the UL. Table 1 listsindicative TDD UL-DL configurations over a period of 10 TTIs which isalso referred to as frame period. “D” denotes a DL TTI, “U” denotes anUL TTI, and “S” denotes a special TTI which includes a DL transmissionfield referred to as DwPTS, a Guard Period (GP), and an UL transmissionfield referred to as UpPTS. Several combinations exist for the durationof each field in a special TTI subject to the condition that the totalduration is one TTI.

TABLE 1 TDD UL-DL configurations. DL-to-UL TDD UL-DL Switch- Configura-point TTI number tion periodicity 0 1 2 3 4 5 6 7 8 9 0 5 ms D S U U U DS U U U 1 5 ms D S U U D D S U U D 2 5 ms D S U D D D S U D D 3 10 ms DS U U U D D D D D 4 10 ms D S U U D D D D D D 5 10 ms D S U D D D D D DD 6 5 ms D S U U U D S U U D

In a Time Division Duplex (TDD) system, a HARQ-ACK signal transmissionfrom a UE in response to PDSCH receptions in multiple DL TTIs may betransmitted in a same UL TTI. A number M of DL TTIs for which associatedHARQ-ACK signal transmissions from UEs are in a same UL TTI is referredto as a bundling window of size M. One consequence of TDD operation isthat a HARQ-ACK signal transmission from a UE or a NodeB in response toa data Transport Block (TB) reception may not occur as early as for FDDwhere both DL signaling and UL signaling can be supported in a same TTIusing different frequencies. Table 2 indicates DL TTIs n−k, where k∈K,for which an HARQ-ACK signal transmission is in UL TTI n. For example,for TDD operation and UL-DL configuration 5, a HARQ-ACK signaltransmission from a UE in response to a data TB reception in TTI number9 occurs after 13 TTIs while for FDD operation a HARQ-ACK signaltransmission from a UE in response to a data TB reception in a TTIalways occurs after four TTIs.

TABLE 2 Downlink association set index: TDD UL-DL TTI n Configuration 01 2 3 4 5 6 7 8 9 0 — — 6 — 4 — — 6 — 4 1 — — 7, 6 4 — — — 7, 6 4 — 2 —— 8, 7, 4, 6 — — — — 8, 7, 4, 6 — — 3 — — 7, 6, 11 6, 5 5, 4 — — — — — 4— — 12, 8, 7, 11 6, 5, 4, 7 — — — — — — 5 — — 13, 12, 9, 8, — — — — — —— 7, 5, 4, 11, 6 6 — — 7 7 5 — — 7 7 —

To accommodate an additional HARQ latency for a TDD system, a respectivemaximum number of HARQ processes needs to be larger than for a FDDsystem. For DL operation and for TDD UL-DL configurations 2, 3, 4, and5, a number of HARQ processes larger than 8 is needed (a number of HARQprocesses of 10, 9, 12, and 15 is needed, respectively) and a respectiveDL HARQ process field in respective DCI formats includes 4 bits while itincludes three bits for a FDD system where a maximum number of DL HARQprocesses is eight.

DL DCI formats (in TDD) also include a DL Assignment Index (DAI) fieldof two bits. A DL DAI is a counter indicating a number for a DL DCIformat a NodeB transmits to a UE in a DL TTI of a bundling window. Thevalue of a DAI field is 1 if a respective DL DCI format is a first one aNodeB transmits to a UE, it is 2 if a DL DCI format is a second one aNodeB transmits to a UE, and so on. Using the value of a DL DAI field, aUE can determine whether it has missed detecting any DCI format in aprevious DL TTI and can incorporate such events in a HARQ-ACK signaltransmission for a respective bundling window. Additionally, UL DCIformats include a UL DAI field informing a UE of a total number of DLDCI formats (PDSCHs or a SPS release) transmitted to a UE in respectiveTTIs of an associated bundling window. Using a value of an UL DAI field,a UE provides HARQ-ACK information in a respective PUSCH for a number ofDCI formats in a respective bundling window. For example, an UL DCIformat can include an UL DAI field of 2 bits with a value of ‘00’indicating inclusion of HARQ-ACK bits for 0 or 4 DL DCI formats (a UEselects 4 if it detected at least one DL DCI format; otherwise, itselects 0), a value of ‘01’, ‘10’ or ‘11’ respectively indicatinginclusion of HARQ-ACK bits for 1 DL DCI format, 2 DL DCI formats, and 3DL DCI formats. Moreover, at least for TDD UL-DL configuration 0including more UL TTIs than DL TTIs, an UL DCI format includes an ULindex indicating whether a PUSCH scheduling applies for a first UL TTI,a second UL TTI, or both a first and a second UL TTIs.

In order to improve utilization of carriers with small BWs or facilitatecommunication over different carrier frequencies, a communication systemmay include an aggregation of several carriers. For example, one carriermay have a BW of 10 MHz while another carrier may have a DL BW of 1.4MHz or one carrier may operate at a frequency of 900 MHz while anothercarrier may operate at a frequency of 3.5 GHz. Then, as a spectralefficiency of PDCCH transmissions is typically low in small DL BWs, itcan be preferable to schedule a PDSCH in a carrier with DL BW of 1.4 MHzfrom a carrier with DL BW of 10 MHz (cross-carrier scheduling). Also, asa path-loss is larger for higher carrier frequencies and controlinformation typically requires higher detection reliability than datainformation and cannot benefit from retransmissions, it can bepreferable to schedule a PDSCH in a 3.5 GHz carrier from a 900 MHzcarrier.

In Carrier Aggregation (CA), each carrier represents a cell. A UE can beconfigured by a NodeB through higher layer signaling more than one cellfor PDSCH receptions (DL CA) or PUSCH transmissions (UL CA). For a UEconfigured with DL CA or UL CA, UE-common control information in arespective PDCCH is transmitted only in a DL of a single cell that isreferred to as primary cell (PCell). Other cells are referred to assecondary cells (SCells). A UE always remains connected to its primarycell while a connection to a secondary cell may be activated ordeactivated.

In CA, it is possible for a NodeB to schedule a UE in a second cell bytransmitting PDCCH in a first cell. This functionality is referred to ascross-carrier scheduling and DCI formats include a Carrier IndicatorField (CIF) having a value corresponding to a respective cell. Forexample, for a CIF consisting of 3 bits and a UE configured with 5cells, respective binary CIF values can be ‘000’, ‘001’, ‘010’, ‘011’,and ‘100’ to indicate each of the 5 cells. In case of a UE configuredwith CA of 2 cells and with cross-carrier scheduling, all PDCCH aretransmitted in the primary cell. CA between a FDD carrier and a TDDcarrier allows for greater flexibility in utilizing TDD and FDDspectrum, improves load balancing without inter-mode hand-over and, fora backhaul connection with negligible delay, it avoids a UCI reportinglatency associated with TDD operation.

FIG. 8 illustrates an example of physical uplink shared channel (PUSCH)resource allocation according to this disclosure. One or moreembodiments of this disclose recognize and take into account chart 800illustrated in FIG. 8. UEs come in a wide variety of configurations, andFIG. 8 does not limit the scope of this disclosure to any particularimplementation of a UE.

As shown in FIG. 8, a UE switches between a frequency 802 of a primarycomponent carrier (PCC) and a frequency of a secondary component carrier(SCC) as time passes. In different embodiment, certain UE architecturesmay only be capable of transmitting on only one uplink carrier frequencyat a time. For example, the UE may only be equipped with a single poweramplifier for transmission or the UE may only be equipped with a singletransmit RF circuit.

It should be noted that methods to enable uplink carrier frequencyswitching to support non-co-channel dual connectivity can also beapplied to an uplink carrier selection scheme. In this embodiment, aneNodeB may be equipped with multiple uplink carriers, and methods areprovided to enable the UE to switch its uplink carrier frequencydepending on the channel or load condition for each carrier.

Abbreviations

ACK Acknowledgement

ARQ Automatic Repeat Request

CA Carrier Aggregation

C-RNTI Cell RNTI

CRS Common Reference Signal

CSI Channel State Information

D2D Device-to-Device

DCI Downlink Control Information

DL Downlink

DMRS Demodulation Reference Signal

EPDCCH Enhanced PDCCH

FDD Frequency Division Duplexing

HARQ Hybrid ARQ

IE Information Element

MCS Modulation and Coding Scheme

MBSFN Multimedia Broadcast multicast service Single Frequency Network

O&M Operation and Maintenance

PCell Primary Cell

PDCCH Physical Downlink Control Channel

PDSCH Physical Downlink Shared Channel

PMCH Physical Multicast Channel

PRB Physical Resource Block

PSS Primary Synchronization Signal

PUCCH Physical Uplink Control Channel

PUSCH Physical Uplink Shared Channel

QoS Quality of Service

RACH Random Access Channel

RNTI Radio Network Temporary Identifier

RRC Radio Resource Control

RS Reference Signals

RSRP Reference Signal Received Power

SCell Secondary Cell

SIB System Information Block

SSS Secondary Synchronization Signal

SR Scheduling Request

SRS Sounding RS

TA Timing Advance

TAG Timing Advance Group

TDD Time Division Duplexing

TPC Transmit Power Control

UCI Uplink Control Information

UE User Equipment

UL Uplink

UL-SCH UL Shared Channel

Aspects, features, and advantages of the one or more embodiments of thisdisclosure are readily apparent from the following detailed description,simply by illustrating a number of particular embodiments andimplementations, including the best mode contemplated for carrying outthe disclosure. The disclosure is also capable of other and differentembodiments, and its several details can be modified in various obviousrespects, all without departing from the spirit and scope of thedisclosure. Accordingly, the drawings and description are to be regardedas illustrative in nature, and not as restrictive. The application isillustrated by way of example, and not by way of limitation, in thefigures of the accompanying drawings.

One or more embodiments provides for uplink carrier switching. In anexample embodiment, a UE is capable of downlink carrier aggregation ordual connectivity such that the UE can receive downlink transmissions onmultiple carrier frequencies simultaneously and only capable oftransmitting on one uplink carrier frequency at a time.

In one situation, at any given time, the UE is only capable oftransmitting on one uplink frequency corresponding to a single uplinkcarrier.

In another situation, at any given time, the UE is only capable oftransmitting on one uplink frequency band which may comprise oftransmission on multiple uplink carriers.

One or more of the embodiments are described in the context of the firstsituation, but it should be understood that embodiments of thedisclosure can also be applied in a straightforward manner to the secondsituation.

When the UE capable of transmitting on only uplink carrier frequency isconfigured with downlink carrier aggregation or dual connectivity, theUE can also be configured with the system information of multiple uplinkcarrier frequencies. In addition, the UE is also configured withUE-specific configurations per uplink carrier. For example, for eachuplink carrier, the UE is configured with the corresponding uplinkcarrier frequency, uplink bandwidth, uplink cyclic prefix length, uplinkpower control configuration, random access resource configuration, SRSconfiguration, CSI feedback configuration, and the like, for example,via RRC signaling.

If the UE is only capable of transmitting at one uplink carrierfrequency at a time, one or more embodiments may provide a method tocontrol the UE's uplink carrier frequency. Time may be needed for the UEto switch uplink radio frequency during which the UE does not transmitsignals, e.g. 0.5 ms may be needed to switch from one carrier frequencyto another. The switching time incurs spectral efficiency loss, hence itmay be considered desirable to minimize the switching frequency.Depending on UE implementation, the time needed for frequency switchingcan also be in the order of microseconds, in which case the switchingtime can be considered to be practically zero and no spectral efficiencyloss is incurred.

FIG. 9 illustrates an example uplink carrier frequency switching pattern900 according to this disclosure. The embodiment of the pattern 900illustrated in FIG. 9 is for illustration only, and the UEs 111-115 ofFIG. 1 could have the same or similar configuration. However, UEs comein a wide variety of configurations, and FIG. 9 does not limit the scopeof this disclosure to any particular implementation of a UE.

As shown in FIG. 9, the pattern 900 includes a primary uplink (p-UL)carrier frequency (f₁) 902, a secondary uplink (s-UL) carrier frequency(f₂) 904, and a switching period 906. In one embodiment, the UE can beconfigured with the pattern 900 and the UE could retune its uplinkcarrier frequency in accordance with the pattern 900.

For example, the UE may tune its carrier frequency to frequency f₁ 902initially and switch its uplink carrier frequency to frequency f₂ 904 ina periodic manner at specified start times and stay at frequency f₂ 904for a specified time period before switching back to frequency f₁ 902.

The initial carrier frequency can be the default uplink carrierfrequency prior to the configuration of the carrier aggregation (e.g.uplink carrier frequency of the primary component carrier or a componentcarrier of a Master eNodeB (MeNB)) or can be configurable by the networkas part of the carrier aggregation configuration, e.g. the uplinkcarrier frequency of the eNodeB controlling a secondary componentcarrier or a component carrier of a Secondary eNodeB (SeNB) can also bethe initial uplink carrier frequency. The initial uplink carrierfrequency may be referred to as the p-UL carrier frequency and thecarrier frequency that the UE switches to periodically as the s-ULcarrier frequency.

Although the disclosure is described using two carrier frequencies, itis only exemplary and the disclosure can be extended to three or morecarrier frequencies in a straightforward manner.

The uplink carrier frequency switching start times can be defined by thesystem frame number (SFN) as well as the subframe offset with respect tothe first subframe of the system frame. In one example, the switching tos-UL carrier frequency starts at a SFN and subframe that meet thefollowing condition:

SFN mod T=FLOOR(ulRfSwitchOffset/10);

subframe=ulRfSwitchOffset mod 10;

where ulRfSwitchOffset and T are configurable by the network. In anexample, ulRfSwitchOffset can be [0 . . . 39] and T can be “4”. Thisenables the UE to switch from p-UL carrier frequency to s-UL carrierfrequency once every four frames. Other example configurations are shownin Table 3. In one approach of uplink carrier frequency switchingpatterns configuration, a table such as Table 3 can be predefined, whereeach Configuration ID defines the periodicity T and the range ofulRfSwitchOffset; and the network can signal or reconfigure theConfiguration ID as well as ulRfSwitchOffset to the UE by higher layersignaling (RRC or MAC) or by dynamic control signaling (usingPDCCH/EPDCCH).

TABLE 3 Uplink carrier frequency switch start time configurationConfiguration ID ulRfSwitchOffset T 1 [0 . . . 39] 4 2 [0 . . . 79] 8 3 [0 . . . 159] 16

Upon switching to s-UL carrier frequency, the UE maintains its uplinkfrequency for a period of Y ms (including the switching period) where Ycan be predefined in the 3GPP standards, e.g. 10 ms or 20 ms. After Yms, the UE switches its uplink frequency back to p-UL carrier frequency.In one example, Y can be configurable by the network via higher layersignaling (e.g. RRC). To provide enhanced flexibility, Y can also beconfigured via MAC or dynamic control signaling (using PDCCH/EPDCCH).

TABLE 4 Time period during which the UE maintains its uplink carrierfrequency at s-UL carrier frequency Configuration # Time period at s-ULcarrier frequency 1 (or A) 10 ms 2 (or B) 20 ms 3 (or C) 40 ms

In another configuration method, the start time and Y can be jointlyconfigured by the network using Configuration ID and ulRfSwitchOffset asshown in Table 5. The network can signal/reconfigure the ConfigurationID as well as ulRfSwitchOffset to the UE by higher layer signaling (RRCor MAC) or by dynamic control signaling (using PDCCH/EPDCCH).

TABLE 5 Joint configuration of uplink carrier frequency switching starttime and stay time Configuration Time period at s-UL ID ulRfSwitchOffsetT (ms) carrier frequency (ms) 1 [0 . . . 39] 40 10 2 [0 . . . 79] 80 203  [0 . . . 159] 160 40

FIG. 10 illustrates an example process 1000 for determining which uplinkcarrier frequency for transmission according to this disclosure. The UEhere may represent the UE 116 in FIGS. 1 and 3. The embodiment of theprocess 1000 shown in FIG. 10 is for illustration only. Otherembodiments of the process 1000 could be used without departing from thescope of this disclosure.

At operation 1002, the UE can be configured with independent parametersrelevant to uplink transmission per uplink carrier frequency. Atoperation 1004, the UE identifies whether the UL carrier frequency isthe p-UL carrier frequency or the s-UL carrier frequency.

At operation 1006, when the UE's uplink carrier frequency is tuned top-UL carrier frequency, the UE shall transmit uplink signals accordingto the configurations for p-UL carrier frequency. At operation 1008,when the UE's uplink carrier frequency is tuned to s-UL carrierfrequency, the UE shall transmit uplink signals according to theconfigurations for s-UL carrier frequency. The configurations relevantto uplink transmission includes SRS, periodic CSI reporting, PUCCH (ifdefined/configured for the carrier), random access resourceconfiguration, uplink power control configuration, and the like.

FIG. 11 illustrates an example uplink carrier frequency switchingpattern 1100 according to this disclosure. The embodiment of the pattern1100 illustrated in FIG. 11 is for illustration only, and the UEs111-115 of FIG. 1 could have the same or similar configuration. However,UEs come in a wide variety of configurations, and FIG. 11 does not limitthe scope of this disclosure to any particular implementation of a UE.

As shown in FIG. 11, the pattern 1100 includes an uplink frequency (f₁)1102, an uplink frequency (f₂) 1104, a downlink frequency (f₁′) 1106,and a downlink frequency (f₂′) 1108. In one embodiment, the UE can beconfigured with the pattern 1100 and the UE could retune its uplinkcarrier frequency in accordance with the pattern 1100.

In one or more embodiments, the UE switches uplink carrier frequencyupon receiving a command from the network. For example, the UE may tuneits carrier frequency to frequency f₁ 1102 initially and switch itsuplink carrier frequency to frequency f₂ 1104 if signaled by the networkto do so.

The UE can be configured by higher layer signaling with the systeminformation and parameters associated with each potential target uplinkcarrier frequency, including an identity for each of the uplink carrierfrequency. Then, the command for uplink carrier frequency switchingincludes the target uplink carrier frequency identity. The number ofsignaling bits can be defined by the number of target uplink carrierfrequencies, e.g. when there are only two possible uplink carrierfrequencies, only a single bit signaling may be used. The smallsignaling overhead makes it suitable to be delivered in a physicaldownlink control channel such as PDCCH or EPDCCH. Nevertheless,deliveries of the switching command by MAC control element or RRC arealso viable options.

Assuming control signaling by PDCCH/EPDCCH, a new DCI format can bedefined to carry the switching command. The DCI can be UE-specific; i.e.it can be sent in the UE-specific search space of the PDCCH/EPDCCH andthe CRC of the PDCCH/EPDCCH can be scrambled with UE's C-RNTI or UE ID.One bit can be introduced in the DCI format (DCI formats for downlinkassignment (e.g. DCI format 2, 2A, 2B, 2C, 2D) or DCI formats for ULgrant (e.g. DCI format 0, 4)) to indicate the switching command. Bitvalue of 0 can mean “don't switch” and bit value of 1 can mean “switch”.In another embodiment, the DCI can also be common for a group of UEs andthe DCI can be sent in the common search space of the PDCCH/EPDCCH. Anew RNTI can also be defined to scramble the CRC of the PDCCH/EPDCCH. Ifthe new DCI format has a different size than the other existing DCIformats that the UE has to monitor, there is a cost of additional blinddecoding to the UE. To overcome this overhead, the DCI can be paddedwith bits such that the final size is the same as that of one of theexisting DCI formats. In another option, the DCI format can reuse thedata structure of one of the existing DCI formats, except that certainbit fields can be fixed to certain values commonly known to both thenetwork and the UE (which can serve as additional protection againstfalse detection).

In carrier aggregation, there is a downlink carrier that is linked toeach uplink carrier, either by SIB-2 or by RRC signaling. In one option,the UE may only be required to monitor the switching command on thedownlink carrier that is linked to the current uplink carrier. This isconsistent with the PDCCH/EPDCCH monitoring behavior described below.

Regardless of the signaling method (RRC, MAC or PDCCH/EPDCCH), time isneeded for the UE to decode and apply the new configuration. In oneembodiment, the UE can immediately apply the new configuration uponsuccessfully decoding the (re)configuration message. A maximum delay toapply the new configuration can also be defined. An advantage of thisbehavior is reduced latency. However, the exact timing of uplink carrierswitching of the UE may be unknown to the network since not all UEs haveexactly the same implementation. It may be desirable to avoid thisambiguity even though it is a temporary one especially if this affectsother UE behavior such as the downlink PDCCH/EPDCCH monitoring behavioras described below. To avoid potential ambiguity, exact timing ofswitching can be defined.

In one example embodiment, the UE applies new configuration after x msof receiving the command, e.g. x ms can be 4 ms or other value that issufficiently large for the UE to process and apply the controlsignaling.

In another example embodiment, the UE applies the new configurationafter x ms of transmitting positive HARQ-ACK to acknowledge successfulreception of the switching command. The x value may take into accountnetwork internal processing delay if inter-eNodeB coordination isinvolved.

To allow for different deployment scenarios (e.g. to accommodatedifferent backhaul type), the delay x can be made configurable by thenetwork.

FIG. 12 illustrates an example of configurable switching period patterns1200 a-b according to this disclosure. The embodiment of the patterns1200 a-b illustrated in FIG. 12 is for illustration only, and the UEs111-115 of FIG. 1 could have the same or similar configuration. However,UEs come in a wide variety of configurations, and FIG. 12 does not limitthe scope of this disclosure to any particular implementation of a UE.

As shown in FIG. 12, the patterns 1200 a-b include a primary uplink(p-UL) carrier frequency (f₁) 1202, a secondary uplink (s-UL) carrierfrequency (f₂) 1204, and a switching period 1206. In one embodiment, theUE can be configured with one of the patterns 1200 a-b and the UE couldretune its uplink carrier frequency in accordance with the pattern 1200a or 1200 b.

In an embodiment, when using pattern 1200 a, the switching period 1206may be 0.5 ms and, when using pattern 1200 b, the switching period 1206may be 1.0 ms. In other embodiments of this disclosure, the switchingperiod 1206 may be other time periods.

In an embodiment, time may be provisioned for the UE to carry out uplinkcarrier frequency switching, e.g. 0.5 ms or 1 ms. During the switchingperiod 1206, the UE does not transmit uplink signals. In one example, ifthe UE switches uplink frequency at the beginning of the first slot ofsubframe x, the UE may start to transmit at the new frequency at thebeginning of the first slot of subframe x+1. In another example, the UEmay start to transmit certain physical signals at the beginning of thesecond slot of subframe x, e.g. the SRS, at the new frequency, but theother physical signals may only be transmitted from subframe x+1.

One or more embodiments provides for uplink timing alignment. If thetime away from a carrier frequency is longer than a specified time, theUE may be required to initiate random access procedure by transmittingphysical random access channel to acquire uplink synchronization afterswitching to the carrier frequency. The UE may only be allowed totransmit other physical signals such as PUCCH/PUSCH/SRS after successfulacquisition of uplink synchronization. In LTE Rel-11, there can be oneTime Alignment Timer (TAT) per Timing Advance Group (TAG). The TAT forthe primary TAG is called pTAG and the TAT for a secondary TAG is calledsTAG. Upon the expiry of the TAT for a TAG, the UE assumes that thecarriers corresponding to the TAG is no longer uplink synchronized andstops uplink transmission. Upon the expiry of the pTAG, the UE shallassume that all carriers (including carriers corresponding to sTAGs) areno longer uplink synchronized. The UE may only be allowed to transmitphysical random access channel on a carrier of a sTAG if initiated bythe network.

When the UE is configured with uplink carrier frequency switchingpattern as described in any of the patterns above, one or moreembodiments may maintain uplink synchronization with carrierscorresponding to p-UL carrier frequency and s-UL carrier frequency. Thecarriers corresponding to p-UL carrier frequency and s-UL carrierfrequency may be configured to be in different TAGs with separate TATs.The TAT for a carrier may continue to run even if the UE does not haveits uplink frequency tuned to the carrier frequency.

Upon switching uplink carrier frequency, the UE checks if the TAT forthe target uplink is still running. If the TAT is not running, the UEshall initiate random access procedure to acquire uplink synchronizationeven if the carrier corresponds to a secondary component carrier,instead of waiting for network to initiate the random access procedure.This reduces time delay to acquire uplink synchronization. For fasteracquisition, the random access resource (preamble and time/frequencyresource) can be configured per uplink carrier to the UE.

In one embodiment, when the UE is configured with dual connectivity,upon the expiry of the pTAG's TAT, the UE may not assume that the TAT(s)of all other carriers corresponding to another eNodeB also expire(s).

FIGS. 13A-13B illustrate example of PDCCH/EPDCCH monitoring behaviorsaccording to this disclosure. The embodiment of the monitoring behaviorsillustrated in FIGS. 13A-13B are for illustration only, and the UEs111-115 of FIG. 1 could have the same or similar behaviors. However, UEscome in a wide variety of configurations, and FIGS. 13A-13B do not limitthe scope of this disclosure to any particular implementation of a UE.

As shown in FIGS. 13A-13B, the pattern 1300 includes uplink frequencies(f₁/f₂) 1302, a downlink frequency (f₁′) 1304, and a downlink frequency(f₂′) 1306. In one embodiment, the UE can be configured with the pattern1300 a or 1300 b and the UE could retune its uplink carrier frequency inaccordance with the pattern 1300 a or 1300 b.

In one or more embodiments, the UE may ignore dynamic or configuredunicast downlink assignment, dynamic or configured uplink assignment,and an aperiodic CSI/SRS request received on a DL carrier that wouldresult in transmission of HARQ-ACK, PUCCH/PUSCH on the uplink carrierlinked (e.g. via SIB2) to the DL carrier at the time when the UE doesnot have its uplink frequency tuned to the uplink carrier concerned.Dynamic downlink/uplink assignment refers to downlink/uplink assignmentwith a corresponding PDCCH/EPDCCH (with CRC scrambled by C-RNTI or UEID) and configured downlink/uplink assignment refers to downlink/uplinkassignment without a corresponding PDCCH/EPDCCH (semi-persistentscheduling (SPS), CRC of the activation PDCCH/EPDCCH is scrambled withSPS-RNTI).

Equivalently, if the UE is configured switch carrier frequency from f₁to f₂ at the beginning of subframe k, the UE could monitor PDCCH/EPDCCHon f₁ for dynamic or configured unicast downlink assignment, dynamic orconfigured uplink assignment, aperiodic CSI/SRS request until andincluding subframe k−m−1. The UE may not need to monitor PDCCH/EPDCCH onf₁ for dynamic or configured unicast downlink assignment, dynamic orconfigured uplink assignment, aperiodic CSI/SRS request from subframek−m until m subframes before the next switching subframe. Meanwhile, theUE may monitor PDCCH/EPDCCH on f₂ for dynamic or configured unicastdownlink assignment, dynamic or configured uplink assignment, aperiodicCSI/SRS request from subframe k−m until m subframes before the nextswitching subframe. One example of this principle is illustrated in FIG.13A where m is assumed to be four subframes. In this example, if theuplink carrier switching occurs at subframe n+6 from frequency f₁ to f₂,the UE stops monitoring the PDCCH/EPDCCH on the downlink carrier that islinked to f₁ (i.e. f₁′) from subframe n+2, and starts monitoring thePDCCH/EPDCCH on the downlink carrier that is linked to f₂ (i.e. f₂′)from subframe n+3 (inclusive). Another example is illustrated in FIG.13B where the UE starts monitoring downlink carrier f₂′ from subframen+2 rather than n+3 to avoid wasting downlink resources. In thisembodiment, the UE shall report HARQ-ACK to any downlink assignmentdetected in subframe n+2 in subframe n+7.

One or more embodiments provide semi-persistent scheduling (SPS). UponUL SPS activation, the UE is required to transmit periodically on thetarget UL carrier frequency until the SPS session is deactivated. TheSPS transmission interval is configurable by the network, e.g. 10, 20,32, 40, 64, 80, 128, 160, 320, 640 ms.

In one embodiment, in order to minimize the uplink carrier switchingfrequency, the UE shall remain tuned to the target uplink carrierfrequency until the SPS is deactivated. The UE can then resume theuplink carrier frequency switching behavior as described in FIG. 9.

In another embodiment, the UE shall remain tuned to the target uplinkcarrier frequency until the SPS is deactivated if the SPS transmissioninterval configured is less than or equal to a certain value. Forexample, the value can be 20 ms or 40 ms.

When there is inter-eNodeB carrier aggregation, the SPS configuration ofthe UE could be exchanged between eNodeBs, including the SPStransmission interval and the timing of SPS activation/deactivation.This enables the eNodeBs to be in-sync about UE's UL carrier switchingstatus.

One or more embodiments provide joint operation of an FDD carrier and aTDD carrier with non-ideal backhaul.

Several additional aspects exist for supporting joint operation or CAbetween an FDD cell and a TDD cell with non-ideal backhaul connection(characterized by one-way latency of more than 10s of ms) between them,regardless of whether the FDD cell or the TDD cell is the primary cell.PUCCH transmission in a secondary cell can generally be an option forUEs configured with aggregation of multiple cells, which can beparticularly beneficial in CA between cells connected with a non-idealbackhaul. In this disclosure, we focus on the case where the UE is notcapable of simultaneous UL transmission or not capable of UL carrieraggregation.

One aspect is a determination of an UL TTI for transmission in the FDDcell of HARQ-ACK information in response to transmissions of DL DCIformats for the FDD cell. Another aspect is a determination for anexistence and dimensioning of various fields in DCI formats for the FDDcell, including a DL HARQ process index field, a DL DAI field, and an ULDAI field.

One or more embodiments recognizes and takes into account that there isa need to determine an UL TTI for transmission in the FDD cell ofHARQ-ACK information in response to transmissions of DL DCI formats forthe FDD cell.

One or more embodiments recognizes and takes into account that there isanother need to determine an existence and dimensioning of variousfields in DCI formats for an FDD secondary cell, including a DL HARQprocess index field, a DL DAI field, and an UL DAI field.

In one or more of the following embodiments, it may be assumed that UCIfor a carrier is transmitted by a UE over the air to an eNodeBassociated with the carrier, either via PUCCH (either on the primarycell or on a secondary cell) or via PUSCH (either on the primary cell oron a secondary cell). While non-negligible backhaul latency betweencells of e.g. more than 10s of ms (one-way) is considered in theexemplary deployment scenarios, it is not a necessary condition for theembodiments that can also apply to deployment scenarios with idealbackhaul between cells.

One or more of the following embodiments consider a UE that is notcapable of UL carrier aggregation but is capable of DL carrieraggregation; i.e. a UE that is not capable of simultaneous transmissionson multiple UL carriers but is capable of simultaneous receptions onmultiple DL carriers. However, a UE may be capable of switching its ULcarrier frequency from one frequency to another in a fraction of amillisecond.

One or more of the following embodiments consider as an exemplaryrealization a single FDD cell (primary cell) and a single TDD cell(secondary cell); extensions to multiple FDD cells (with one FDD primarycell) or multiple TDD secondary cells are straightforward and areomitted for reasons of brevity and simplicity.

A UE without UL CA capability may not be able to transmit simultaneouslyin different carrier frequencies. If the UE is configured with DLcarrier aggregation of a FDD cell (Primary cell) and a TDD cell(secondary cell) and there is non-ideal backhaul connection between thetwo cells, both the FDD cell and the TDD cell require uplinktransmission from the UE (in a different UL carrier for each cell) todeliver UL control information and UL data for the respective cell. Thisimplies that a UE without UL CA capability may switch its UL carrierfrequency between the two cells. One or more embodiments of thisdisclosure provide an UL frequency switching behavior between cells fora UE so that a network and the UE have a same understanding on when theUE can transmit on an UL frequency.

FIGS. 14A-14B illustrate example of PUSCH in subframes 1400 a-baccording to this disclosure. The embodiment of the monitoring behaviorsillustrated in FIGS. 14A-14B are for illustration only, and the UEs111-115 of FIG. 1 could have the same or similar behaviors. However, UEscome in a wide variety of configurations, and FIGS. 14A-14B do not limitthe scope of this disclosure to any particular implementation of a UE.

As shown in FIGS. 14A-14B, the subframes 1400 include slots 1402,symbols 1404, reference signals 1406, resource elements 1408, and uplinkswitching time periods 1410. In one embodiment, the UE can be configuredwith the subframes 1400 a or 1400 b and the UE could retune its uplinkcarrier frequency in accordance with the subframes 1400 a or 1400 b.

In an embodiment, in a UE hardware implementation, the UL frequencyswitching takes a fraction of a millisecond. Depending on how efficientthe UE implementation is, the UL frequency switching duration may be asshort as less than an OFDM symbol duration (i.e., less than 0.5/7 ms),or as long as about a time slot (i.e., 0.5 ms). When designing aprotocol, a typical UE hardware implementation efficiency should betaken into account.

As long as the UL frequency switching duration is longer than the CPlength, the UL frequency switching could be explicitly considered in theprotocol. A subframe in which a UE applies UL frequency switching from aTDD carrier to a FDD carrier (D->D/S->D/U for FDD) is referred to asS_(TF) subframe (e.g. subframe 1400 b); and a subframe in which a UEapplies UL frequency switching from a FDD carrier to a TDD carrier(D/U->D/S->D for FDD) is referred to as S_(FT) subframe (e.g. subframe1400 a). It is noted that the UL frequency switching duration can be thesame, regardless of whether the switching is from FDD to TDD or from TDDto FDD.

In one example, the protocol allows UL frequency switching duration nolonger than 0.5 ms. Then, the first slot (0.5 ms) of the S_(FT) subframe(assuming switching begins at the beginning of the second slot of theD/S subframe) and the second slot (0.5 ms) of the S_(TF) subframe(assuming switching begins at the beginning of the D/S subframe) can beavailable for UL transmission in the FDD carrier. While PUCCH/PUSCH maynot be able to be transmitted using only one slot (half subframe), SRScan still be transmitted in the last SC-FDM symbol of the subframe inthe S_(TF) subframe. Alternatively, PUCCH/PUSCH can also be transmittedonly in one slot (the first slot for the S_(FT) subframe and the secondslot for the S_(TF) subframe or, in general, in a number of subframesymbols available for UL transmission), possibly while also increasing,for example doubling, a transmission power in order to offset some ofthe performance loss that occurs from not transmitting in the firstslot. A Transport Block Size (TBS) indicated in DCI formats for UL grantfor the one-slot PUSCH can also be scaled to account for the fact thatthe PUSCH transmission will be over a reduced number of transmissionsymbols. For example, assuming that half the transmission symbols areavailable in a slot compared to a subframe that includes two slots, theTBS indicated by a respective DCI format can be scaled by a factor of0.5. For example, if N_(symb,max) ^(PUSCH) is a maximum number oftransmission symbols for data in a subframe and N_(symb,reduced)^(PUSCH) is a number of transmission symbols for data after switchingthe UL carrier frequency, a TBS signaled in a DCI format can be scaledby N_(symb,reduced) ^(PUSCH)/N_(symb,max) ^(PUSCH) or by a fixed valuesuch as 0.5 if the UL data transmission is approximately over one slot.

In another example, the protocol allows for two different UEimplementations for two categories of UEs. One category of UEs canperform UL frequency switching within 0.5 ms, while the other categoryof UEs cannot perform UL frequency switching within 0.5 ms. In thiscase, for the UEs who can perform UL frequency switching within 0.5 mscan transmit SRS, while the other type of UEs cannot transmit SRS in theS_(TF) subframe. In order to facilitate the network to differentiatethese two types of UEs, a UE capability signaling can be introduced, sothat the network can be aware of UE capability before deciding whetherto schedule SRS transmission for the UE in respective S_(TF) subframes.

If UL frequency switching can be performed within microseconds, i.e.within X SC-FDM symbols (e.g. one or two or three SC-FDM symbols), amajority of UL resource loss in D/S subframes can be recovered if PUCCHand/or PUSCH are also defined for D/S subframes for the remainingN_(symb) ^(PUSCH)−X symbols.

In one example, the protocol allows UL frequency duration no longer thanan SC-FDM symbol duration (i.e., less than 0.5/7 ms, X=1). During theS_(FT) subframe as shown in FIG. 14A, the last SC-FDM symbol is used forUL frequency switching. During the S_(TF) subframe as shown in FIG. 14B,the first SC-FDM symbol is used for UL frequency switching. In thiscase, (N_(symb) ^(PUSCH)−1) SC-FDM symbols are available for ULtransmissions. In another example, a UE is allowed to transmit PUSCHand/or PUCCH transmissions in each of S_(TF) and S_(FT) subframes as ifcell-specific SRS is configured in the S_(FT) subframe; however, the UEis not allowed to transmit SRS in the subframe. For S_(TF) subframes,PUCCH format 2 can be transmitted with the first SC-FDM symbolconsidered punctured. PUCCH formats 1a/1b/3 can also be transmitted ifshorter time-domain orthogonal covering code (OCC) (one symbol shorter)is used; however it would not be possible to multiplex conventional UEswith the UEs employing the shorter OCC. In another method for S_(TF)subframes, a UE is allowed to transmit PUCCH format 2 (with the firstSC-FDM symbol considered punctured), but PUCCH format 1a/1b/3 cannot betransmitted.

FIG. 15 illustrates an example process 1500 for determining an uplinkTTI switching pattern for FDD and TDD joint operation according to thisdisclosure. The UE here may represent the UE 116 in FIGS. 1 and 3. Theembodiment of the process 1500 shown in FIG. 15 is for illustrationonly. Other embodiments of the process 1500 could be used withoutdeparting from the scope of this disclosure.

In one or more embodiments, an UL frequency switching behavior isdetermined by the TDD UL-DL configuration of the TDD cell. For example,a UE tunes its UL frequency to the FDD cell by default and switches tothe UL frequency of the TDD cell during a special subframe of the TDDcell in which the TDD cell switches from DL to UL; the UE switches itsUL frequency to the FDD cell when the TDD cell switches from UL to DL.Table 6 shows the subframes within a frame that a UE identifies as DLand UL subframes for the FDD cell. As shown in Table 6, for every TDDUL-DL configuration, there is a corresponding FDD UL-DL configurationthat determines a UE's interpretation of DL subframes (denoted as D), ULsubframes (denoted as U) as well as subframes where the UE performs ULfrequency switching (denoted as S, which can be S_(TF) or S_(FT) as inEmbodiment 1). Referring again to Table 6, when a UE is configured withTDD UL-DL configuration 2 for the TDD cell, the FDD UL-DL configurationis implicitly determined by the UE to be Configuration 2. In the FDDcell, subframes 4, 5, and 9 are both DL and UL subframes (D/U),subframes 1, 3, 6, 8 are DL subframes and UL switching subframes (D/S)where a UE can receive in the DL and switches its UL frequency, andsubframes 2 and 7 are DL only subframes (D).

Note that for the example in Table 6, TDD UL-DL configuration 0 does nothave the corresponding FDD UL-DL configuration as there would be no ULsubframes for the FDD cell. To enable a FDD UL-DL configuration for TDDUL-DL configuration 0, the DL/UL/S subframe pattern can be modified toenable at least one UL subframe for the FDD cell. For example, subframe9 of the TDD cell to be changed from a U subframe to a switchingsubframe (denoted S′ to differentiate from the special subframe S ofTDD) and the modified TDD UL-DL configuration is referred to as TDDUL-DL configuration 0′. This allows subframe 9, 0, and 1 of the FDD cellto be D/S, D/U and D/S, respectively, so that there is at least one ULsubframe available for FDD UL-DL configuration 0, as shown in Table 8.In another example, subframe 4 and 9 of the TDD cell to be changed froma U subframe to a switching subframe (again, denoted S′ to differentiatefrom the special subframe S of TDD) and the modified TDD UL-DLconfiguration is referred to as TDD UL-DL configuration 0″. This allowssubframes {1,4,6,9} and {0,5} of the FDD cell to be D/S and D/U,respectively, so that there is at least one UL subframe available forFDD UL-DL configuration OA, as shown in Table 8. In yet another example,if PUCCH/PUSCH/SRS is defined on the D/S subframes as described above,TDD UL-DL configuration 0 can be the same as the legacy configuration,and subframes {0,1,5,6} can be defined as the D/S subframes for the FDDcell.

If the TDD UL-DL configuration is reconfigured, e.g. to adapt to dynamictraffic, the FDD UL-DL configuration is also reconfigured accordingly.Hereafter, a UE that performs the described UL frequency switchingbehavior is referred to as being configured or enabled with FDD UL-DLconfiguration.

TABLE 6 FDD UL-DL configuration TDD UL-DL FDD UL-DL TTI/subframe numberConfiguration configuration 0 1 2 3 4 5 6 7 8 9 0 N/A — — — — — — — — —— 1 1 D/U D/S D D D/S D/U D/S D D D/S 2 2 D/U D/S D D/S D/U D/U D/S DD/S D/U 3 3 D/U D/S D D D D/S D/U D/U D/U D/U 4 4 D/U D/S D D D/S D/UD/U D/U D/U D/U 5 5 D/U D/S D D/S D/U D/U D/U D/U D/U D/U 6 6 D/U D/S DD D D D D D D/S

TABLE 7 Modification to TDD UL-DL configuration 0 (denoted 0′ and 0″)DL-to-UL TDD UL-DL Switch-point TTI number Configuration periodicity 0 12 3 4 5 6 7 8 9 0′  5 ms D S U U U D S U U S′ 0″ 5 ms D S U U S′ D S U US′

TABLE 8 FDD UL-DL configuration 0, 0A, OB TDD UL-DL FDD UL-DLTTI/subframe number Configuration configuration 0 1 2 3 4 5 6 7 8 9 0′ 0   D/U D/S D D D D D D D D/S 0″ 0A D/U D/S D D D/S D/U D/S D D D/S 0 0B D/S D/S D D D D/S D/S D D D

Referring to FIG. 15, in determining the UL transmission behavior for ajoint operation of a FDD carrier and a TDD carrier, at operation 1502, aUE considers whether FDD UL-DL configuration is enabled or not. Ifenabled, at operation 1504, the FDD UL-DL configuration of the FDD cellis implicitly determined from the TDD UL-DL configuration of the TDDcell and the UE performs UL frequency switching according to the FDDUL-DL configuration and the TDD UL-DL configuration. Otherwise, atoperation 1506, the UE operates in the FDD cell in a conventionalmanner.

In an embodiment, a UE may not transmit signals in the UL for DL-onlysubframes. Table 9 shows a percentage of UL resource loss in a FDD cell.In a deployment scenario where the FDD cell is a macro cell and the TDDcell is a small cell (e.g. pico/femto cell), the loss of UL resourcesfor FDD may be tolerable if most of the UE traffic is routed via the TDDcell. In addition, a network can adapt to an UL resource need of the FDDcell by reconfiguring the TDD UL-DL configuration and the FDD UL-DLconfiguration. For example, reconfiguring from TDD UL-DL configuration 2to TDD UL-DL configuration 5 reduces the UL resource loss of the FDDcell from 60% to 30%.

TABLE 9 % UL resource loss to FDD cell FDD UL-DL % UL resource loss toFDD configuration cell 0 90% 1 60% 2 60% 3 50% 4 40% 5 30% 6 90%

In another example embodiment, the FDD UL-DL configuration is explicitlysignaled by the network. An UL transmission and frequency switchingpattern is predefined for each FDD UL-DL configuration. Relying on theFDD UL-DL configuration, a UE may derive the TDD UL-DL configuration,even if the UE does not receive an explicit signaling of the TDD UL-DLconfiguration. For example, if the UE receives FDD UL-DL configuration 2for the FDD (primary) cell, the UE may derive that the TDD UL-DLconfiguration for the TDD (secondary) cell is TDD UL-DL configuration 2(according to Table 6).

In yet another example embodiment, both FDD UL-DL configuration and TDDUL-DL configuration are signaled by the network. When a same subframefor the two configurations has conflicting behavior such as, for exampleit is an UL subframe for both the FDD and the TDD UL-DL configurations,a rule can be predefined to resolve such conflict. In one example, theUE may be required to follow the FDD configuration because it is oftenthe primary cell. In another example, the UE may be required to followthe configuration of the cell that is the primary cell. If the TDD cellis the primary cell, the UE shall follow the TDD configuration.

One or more embodiments provide UL HARQ-ACK timing and UL grant timingfor FDD in FDD and TDD joint operation.

A UE may not be expected to be scheduled or configured to transmit onsubframes that correspond to DL-only subframes or D/S subframes. Sincethe UE is supposed to transmit UL HARQ-ACK (in a PUCCH or in a PUSCH)for every unicast PDSCH it received and PUSCH for every UL DCI format itdetected, there is a need to define a method to ensure PUCCH or PUSCHtransmissions in subframes where UL transmissions are allowed (i.e., D/Usubframes) in the FDD cell. Although in the following an HARQ-ACKtransmission by a UE is considered to be in response to a respectivePDSCH reception, it can also be in response to a DL DCI format releasinga previously SPS PDSCH (SPS release) but, for brevity, this will not beadditionally mentioned.

In an example, a conventional UL HARQ-ACK timing and a conventional ULDCI format transmission timing of the FDD cell are maintained. Thisimplies that a restriction should be imposed for unicast PDSCH and forPUSCH scheduling so that the UE does not need to transmit any UL signalsin D and D/S subframes. Referring to Table 10, a UE can report ULHARQ-ACK and transmit PUSCH only if a PDSCH and an UL DCI format,respectively, are detected in the bracketed subframes, wherein thebracketed subframes are determined depending on the FDD UL-DLconfiguration. A first implication is that on subframes that are notbracketed, the UE can be allowed to skip PDCCH decoding for DL DCIformats and UL DCI formats. A second implication is that a number ofHARQ processes for the FDD cell can be reduced. Table 11 shows a maximumnumber of HARQ processes for the FDD cell where the maximum numberdepends on the FDD UL-DL configuration. This approach has the advantagethat a conventional FDD HARQ timing is unchanged; however the schedulingrestriction also means that unicast DL throughput is reduced.

TABLE 10 Subframes (bracketed) where DL assignment and UL grant can bereceived on the FDD cell TDD UL-DL FDD UL-DL TTI/subframe numberConfiguration configuration 0 1 2 3 4 5 6 7 8 9  0′ 0 (Table 8) D/U D/SD D D D [D] D D D/S 1 1 D/U [D/S] D D D/S D/U [D/S] D D D/S 2 2 [D/U][D/S] D D/S D/U [D/U] D/S D D/S D/U 3 3 D/U D/S [D] [D] [D] [D/S] [D/U]D/U D/U D/U 4 4 D/U [D/S] [D] [D] [D/S] [D/U] [D/U] D/U D/U D/U 5 5[D/U] [D/S] [D] [D/S] [D/U] [D/U] [D/U] D/U D/U D/U 6 6 D/U D/S D D D D[D] D D D/S

TABLE 11 Maximum number of HARQ processes for FDD assuming Table 10 FDDUL-DL Maximum number of HARQ configuration processes 0 (Table 8) 1 1 2 23 3 5 4 6 5 7 6 1

In another example, in order to minimize DL throughput loss on the FDDcell, UL HARQ-ACK timing for FDD is modified so that a UE can transmitHARQ-ACK, in response to a PDSCH received in subframe n, in an availableUL subframe n+k where k>4. The maximum number of HARQ processes can bekept as eight using this approach.

In an example embodiment of this example, a UE transmits HARQ-ACK in afirst available UL subframe in order to minimize HARQ-ACK transmissionlatency. An example is given in Table 12 where a UE transmits a HARQ-ACKsignal in subframe n in response to a PDSCH reception in subframe n-kwhere k∈K_(FDD) and K_(FDD):{k₀, k₁, . . . , k_(M) _(FDD) ⁻¹} is calledthe DL association set index and M_(FDD) is the HARQ-ACK bundling windowsize for the FDD cell.

TABLE 12 Downlink association set index K_(FDD): {k₀, k₁, . . . , k_(M)_(FDD) ⁻¹}: FDD UL-DL TTI/subframe n Configuration 0 1 2 3 4 5 6 7 8 9 0(Table 8) 13, 12, 11, 10, — — — — — — — — — 9, 8, 7, 6, 5, 4 1 8, 7, 6,5, 4 — — — — 8, 7, 6, 5, 4 — — — — 2 4 — — — 7, 6, 5, 4 4 — — — 7, 6, 5,4 3 4 — — — — — 9, 8, 7, 6, 5, 4 4 4 4 4 4 — — — — 8, 7, 6, 5, 4 4 4 4 45 4 — — — 7, 6, 5, 4 4 4 4 4 4 6 13, 12, 11, 10, — — — — — — — — — 9, 8,7, 6, 5, 4

Although the DL association set index in Table 12 minimizes latencybetween a DL subframe that a UE receives a PDSCH and an UL subframe theUE transmits respective HARQ-ACK information, it results in an imbalanceof HARQ-ACK information payloads transmitted in respective UL TTIs. Forexample, for FDD UL-DL configuration 4, HARQ-ACK informationcorresponding to detection of data TB s for up to 5 DL subframes istransmitted in UL subframe 5 while HARQ-ACK information corresponding todetection of data TBs for up to 1 DL subframe is transmitted in ULsubframe 0, 6, 7, 8 and 9. This imbalance can result to unequalreception reliability for HARQ-ACK information transmitted in differentUL subframes and unequal respective coverage.

In another example embodiment of this example, a determination of a DLassociation set index for a FDD cell considers balancing a HARQ-ACKinformation payload for the FDD cell. One example is given in Table 13where, for example for Configuration 3, the HARQ-ACK payload of subframe6 in Table 10 is distributed to subframes 6, 7, 8, 9 and 0. Anotherexample is given in Table 14 where HARQ-ACK for adjacent DL subframes isgrouped in a single transmission. In both examples, for FDD UL-DLconfiguration 2, the HARQ-ACK bundling window size in UL subframe 4 and9 is reduced from 4 to 3 while the HARQ-ACK bundling window size in ULsubframe 0 and 5 is increased from 1 to 2 so that the HARQ-ACKinformation payload is more balanced across subframes.

TABLE 13 Downlink association set index K_(FDD): {k₀, k₁, . . . , k_(M)_(FDD) ⁻¹}: FDD UL-DL TTI n Configuration 0 1 2 3 4 5 6 7 8 9 0 (Table8) 13, 12, 11, 10, 9, — — — — — — — — — 8, 7, 6, 5, 4 1 8, 7, 6, 5, 4 —— — — 8, 7, 6, 5, 4 — — — — 2 5, 4 — — — 7, 6, 5 5, 4 — — — 7, 6, 5 3 8,4 — — — — — 9, 8 8, 4 8, 4 8, 4 4 4 — — — — 8, 7 7, 4 7, 4 7, 4 4 5 4 —— — 7, 6 5, 4 5, 4 4 4 4 6 13, 12, 11, 10, 9, — — — — — — — — — 8, 7, 6,5, 4

TABLE 14 Downlink association set index K_(FDD): {k₀, k₁, . . . , k_(M)_(FDD) ⁻¹}: FDD UL-DL TTI n Configuration 0 1 2 3 4 5 6 7 8 9 0 (Table8) 13, 12, 11, 10, 9, — — — — — — — — — 8, 7, 6, 5, 4 1 8, 7, 6, 5, 4 —— — — 8, 7, 6, 5, 4 — — — — 2 5, 4 — — — 7, 6, 5 5, 4 — — — 7, 6, 5 3 5,4 — — — — — 9, 8 8, 7 7, 6 6, 5 4 4 — — — — 8, 7 7, 6 6, 5 5, 4 4 5 4 —— — 7, 6 5, 4 5, 4 4 4 4 6 13, 12, 11, 10, 9, — — — — — — — — — 8, 7, 6,5, 4

Combinations of the above example embodiments for a determination of aDL association set index K_(FDD) for a FDD cell (which for some FDDUL-DL configuration is same between the example and the other example)can also be considered depending on a FDD UL-DL configuration. Forexample, for FDD UL-DL configuration 2, Table 12 can be considered whilefor FDD UL-DL configuration 3, Table 13 or Table 14 can be considered.Moreover, it is noted that unlike the ordering of DL subframes in Table2 for reporting respective HARQ-ACK information for a TDD cell, anordering of DL subframes for reporting respective HARQ-ACK informationfor a FDD cell is according to the order of the DL subframes. This isbecause for special DL subframes in a TDD cell, a DL subframe with asame index is a normal DL subframe in a FDD cell.

In an embodiment, the maximum HARQ-ACK information payload in an ULsubframe of a FDD cell can be determined by the HARQ-ACK bundling windowsize, M_(FDD) the downlink transmission mode, and n other relevant RRCconfiguration parameter(s), where n=0, 1, 2 for example. When M_(FDD)=1,a UE shall use either Format 1a or Format 1b to transmit the HARQ-ACKpayload. When 2≤M_(FDD)≤4, a UE shall use PUCCH format 1b with channelselection to convey the HARQ-ACK payload. When M_(FDD)>4, a UE can useeither PUCCH format 3 or PUCCH format 1b to convey the HARQ-ACK payload.In general, a UE transmits HARQ-ACK in a PUCCH of the FDD cell as incase of a TDD cell with M_(TDD) replaced by M_(FDD).

For FDD UL-DL configuration 1, M_(FDD) is 5 for UL subframe 0 and 5.Assuming that a downlink transmission mode supporting one data transportblock is configured and assuming that HARQ-ACK compression techniquestime-domain bundling are not applied, the PUCCH format that can be usedto carry the HARQ-ACK payload is PUCCH format 3 (PUCCH format 1b withchannel selection is not possible since M_(FDD)>4). To enable PUCCHformat 1b with channel selection to be used in this case, an embodimentmay reduce M_(FDD) to 4. In an example of an embodiment, a networkscheduling restriction can be imposed so that can be assumed to be 4.For example, the network can only schedule in subframe n-k wherek∈{7,6,5,4}. In another example of the embodiment, HARQ-ACK bundling canbe applied to two of the five subframes. For example, time-domainHARQ-ACK bundling can be applied using the logical AND operation onsubframe n-4 and n-5. The above examples can be applied to other caseswhere reduction of would enable more PUCCH formats (that can bepreferred because of superior reliability) to be available for carryingthe HARQ-ACK payload. For example, the above approaches can also beapplied to subframe 4 FDD UL-DL configuration 2 of Table 13 or Table 14so that the maximum HARQ-ACK payload can be capped at 4 assuming adownlink transmission mode that supports two transport blocks isconfigured.

In an embodiment, the maximum number of HARQ-ACK information payload canbe reduced further for the FDD cell if HARQ-ACK compression techniquessuch as spatial-domain bundling (bundling across codewords for DLtransmission modes supporting two transport blocks) and/or time-domainbundling (bundling across subframes, per codeword) are applied orconfigured to the UE. For time-domain bundling, logical AND operationcan be performed on the HARQ-ACKs corresponding to subframe n-k wherek∈{k₀, k₁, . . . , k_(M) _(FDD) ⁻¹}. In this case, the HARQ-ACK payloadsize is reduced to only up to 2 bits per subframe (1 bit fortransmission mode with one transport block) and PUCCH format 1b can beused to carry the HARQ-ACK payload (or PUCCH format 1a for transmissionmode with one transport block). Partial time-domain bundling is alsopossible by bundling only a subset subframes in the set {k₀, k₁, . . . ,k_(M) _(FDD) ⁻¹}, e.g. for FDD UL-DL configuration 6, {13,12,11,10,9}and {8,7,6,5,4} can be bundled separately. For spatial-domain bundling,logical AND operation can be performed on the HARQ-ACKs acrosscodewords, per subframe. A combination of time-domain bundling andspatial-domain bundling is also possible.

One or more embodiments provides benefit if HARQ-ACK payload iscompressed such as only up to 4 bits HARQ-ACK payload is needed to betransmitted in a subframe. In an example, PUCCH format 3 may not be usedor configured for the FDD cell. This can be achieved with time-domainbundling or spatial domain bundling or a combination of both techniques.

FIG. 16 illustrates an example process 1600 for determining the numberof bits for a DL HARQ process index field of an FDD cell according tothis disclosure. The UE here may represent the UE 116 in FIGS. 1 and 3.The embodiment of the process 1600 shown in FIG. 16 is for illustrationonly. Other embodiments of the process 1600 could be used withoutdeparting from the scope of this disclosure.

One or more embodiments provides a DL HARQ process field, DL DAI field,and UL DAI Field in respective DCI formats for a FDD cell in case of aFDD and TDD joint operation.

When a UE is configured with a TDD cell and a FDD cell with FDD UL-DLconfiguration as described above, a transmission timing of UL HARQ-ACKinformation in a PUCCH in response to detecting one or more DL DCIformats for the FDD cell is determined by an availability of ULsubframes in the FDD cell and, unlike conventional FDD operation, itcannot occur in every subframe. Therefore, a bundling window size fortransmission of HARQ-ACK information in response to detecting one ormore DL DCI formats can be larger than 1. Due to an additional latencyrequired for a UE to report HARQ-ACK information in response todetecting one or more DL DCI formats for the FDD cell, a larger numberof DL HARQ processes for PDSCH transmissions in the FDD cell needs to besupported compared to the case of a legacy FDD cell. For example,considering a delay of 3 subframes between an end of a PDSCHtransmission from a NodeB and an availability of a respective HARQ-ACKinformation at a UE, a delay of 4 subframes between a beginning of aHARQ-ACK transmission at a UE and an availability of a schedulingdecision for a same HARQ process at a NodeB, and a delay of up to 13subframes for reporting HARQ-ACK information in the case of FDD UL-DLconfiguration 0 and 6 (as indicated in Table 12, Table 13 and Table 14),a maximum delay of 17 subframes can occur thereby necessitating a use of17 HARQ processes. Table 15 shows the maximum number of HARQ processesfor each FDD UL-DL configuration.

In a situation of CA between a TDD cell and a FDD cell, a DL HARQprocess index field in a DL DCI format for the FDD secondary cellincludes a larger number of bits than in case of a legacy FDD cell(including single-cell FDD operation). In one method, this number ofbits for the DL HARQ process index field can be 5, to support up to 17HARQ processes. However, only FDD UL-DL configuration 0 and 6 needs 17HARQ processes and many of the 5-bit DL HARQ process index field are notused.

In another embodiment, the maximum number of HARQ processes for FDDUL-DL configuration 0 and 6 is defined to be 16, hence the number ofbits for the DL HARQ process index field can be 4 (same as the one forthe DL HARQ process index field in a DL DCI format for a TDD cell). ForFDD UL-DL configuration 0 and 6, the UE assumes only up to 16 HARQprocesses. This method is illustrated in FIG. 16.

Referring to FIG. 16, in detecting a DL DCI format for a FDD cell, atoperation 1602, a UE considers whether FDD UL-DL configuration isenabled. If enabled, at operation 1604, a DL HARQ process index field ina DL DCI format for the UE includes 4 bits; else, at operation 1606, aDL HARQ process index field in a DL DCI format for the UE includes 3bits. In yet another method, the number of bits for the DL HARQ processindex field can depend on the FDD UL-DL configuration. For example, thenumber of bits for the DL HARQ process index field is 5 if FDD UL-DLconfiguration 0 and 6 is configured and the number of bits for the DLHARQ process index field is 4 otherwise.

TABLE 15 Maximum number of HARQ processes for FDD cell Maximum number ofHARQ processes FDD UL-DL configuration according to Table 9 or Table 10or Table 11 0 (Table 8) 17 1 12 2 11 3 13 4 12 5 11 6 17

Similar to the DL HARQ process index field, as transmission of HARQ-ACKinformation from a UE cannot typically occur in successive TTIs, arespective bundling window size for a FDD cell can be larger than 1 TTI.Therefore, in case FDD UL-DL configuration is enabled, a DL DCI formatfor the FDD cell needs to include a DL DAI field that functions as acounter of a DL DCI format in a bundling window similar to the DL DAIfield in DL DCI format for a TDD cell. This existence of a DL DAI fieldin a DL DCI format in case of a TDD cell, in conjunction with an equalsize for a DL HARQ process index field in DL DCI formats for the TDDcell and a FDD cell, result to a DL DCI format having a same sizeregardless of whether it is intended for a TDD cell or a FDD cell. It isnoted that a DL DAI field for a FDD cell can include 2 bits even thoughcan be larger than 4 and a UE can determine an index for a respective DLDCI format in a bundling window based on an index of a last detected DLDCI format within a same bundling window. For example, a DL DAI fieldbinary value of ‘00’ can map either to a DL DCI format index of either1, or 5 (if applicable), or (if applicable) 9 within a same bundlingwindow and a UE can determine a value of 5 if it previously detected asingle DL DCI format including a DL DAI field with binary value of ‘01’,or ‘10’, or ‘11’.

FIG. 17 illustrates an example process 1700 for determining an existenceof a DL DAI field in a DL DCI format depending on whether a primary cellis an FDD cell or a TDD cell according to this disclosure. The UE heremay represent the UE 116 in FIGS. 1 and 3. The embodiment of the process1700 shown in FIG. 17 is for illustration only. Other embodiments of theprocess 1700 could be used without departing from the scope of thisdisclosure.

Referring to FIG. 17, in detecting a DL DCI format for a FDD cell or aTDD cell, at operation 1702, a UE considers whether FDD UL-DLconfiguration is enabled or not. If enabled, at operation 1704, a DL DAIfield is included in a DL DCI format for the UE. Otherwise, at operation1704, the UE operates in the FDD cell in the legacy manner and a DL DAIfield is not included in a DL DCI format for the UE.

For operation in a FDD cell, an UL DAI field indicating to a UE tomultiplex HARQ-ACK information in a PUSCH transmission may not need tobe included in an UL DCI format scheduling the PUSCH transmission. Thisis because HARQ-ACK information is generated in response to a DL DCIformat that is transmitted in a same TTI (and in a same cell) as an ULDCI format scheduling a PUSCH transmission, and therefore it is highlylikely that a UE either detects both DCI formats or misses both DCIformats, and because HARQ-ACK information in response to a DL DCI formatdetection in a previous TTI is already transmitted in a respectiveprevious PUSCH or PUCCH. Therefore, an additional explicit indication toa UE, through a use of an UL DAI field in an UL DCI format, to multiplexHARQ-ACK information in a PUSCH transmission is not essential.

For operation with UL frequency switching, HARQ-ACK information inresponse to a detection of DL DCI format for a FDD cell in a previousTTI may not be transmitted prior to a TTI where a UE transmits a PUSCHin a FDD cell. This is because a respective UL TTI may not exist for theFDD UL-DL configuration in order for a UE to transmit that HARQ-ACKinformation in a PUCCH or because a UE may not have a PUSCH transmissionin a previous TTI in order to multiplex that HARQ-ACK information in thetransmitted PUSCH. Therefore, a PUSCH transmission in a FDD cell mayneed to include HARQ-ACK information in response to detections of DL DCIformats, in respective TTIs prior to the TTI of an UL DCI formatdetection scheduling the PUSCH transmission. It is noted that an UL DAIfield for a FDD cell (with FDD UL-DL configuration) can include 2 bitseven though can be larger than 4 and a UE can determine a number ofHARQ-ACK information bits to multiplex based on a value of the UL DAIfield and also based on a number of detected DL DCI formats within asame bundling window.

FIG. 18 illustrates an example process 1800 for determining an existenceof an UL DAI field in a DL DCI format depending on whether a FDD UL-DLconfiguration is enabled or not according to this disclosure. The UEhere may represent the UE 116 in FIGS. 1 and 3. The embodiment of theprocess 1800 shown in FIG. 18 is for illustration only. Otherembodiments of the process 1800 could be used without departing from thescope of this disclosure.

Referring to FIG. 18, in detecting an UL DCI format for a FDD cell, atoperation 1802, a UE considers whether FDD UL-DL configuration isenabled or not. If enabled, at operation 1804, an UL DAI field isincluded in an UL DCI format for the UE. Otherwise, at operation 1806,the UE operates with a legacy FDD cell, an UL DAI field is not includedin an UL DCI format for the UE.

Upon detection of an UL DCI format that includes an UL DAI field with avalue of V_(DAI) ^(UL) and schedules a PUSCH in a TTI where a UE canmultiplex HARQ-ACK information in a PUCCH, a UE multiplexes in the PUSCHO_(FDD)·min(V_(DAI) ^(UL),M_(FDD)) if PUCCH format 3 is configured) forthe FDD cell, where O_(FDD) is the maximum number of HARQ-ACK bits persubframe for the FDD cell. A UE can determine an association between aDL TTI and respective HARQ-ACK information from a value of a DL DAIfield in each detected DCI format.

One or more embodiments provide UL switching as a function of UE BufferStatus Report (BSR).

In order to facilitate the UL switching configuration as describedabove, it can be beneficial for a network node controlling the RRCconfiguration of the UE (typically the eNodeB controlling the primarycell) to obtain the UE's buffer status report(s) for the othercarrier(s). In this way the network can make an appropriate decision onthe TDD UL-DL configuration and the FDD UL-DL configuration for the UE.The UE's buffer status reports for the other carriers can be obtainedvia X2 signaling from the other eNodeBs or directly from the UE if theBSRs for multiple carriers are transmitted at least on the primary cell.

The UL switching behavior can also be determined implicitly by the UE'sbuffer status for each carrier. If the UE does not have any data in itsbuffer for a particular carrier, the UE does not need to switch to thecorresponding UL carrier frequency for UL data transmission other thanto transmit HARQ-ACK, CSI and SRS. Therefore, based on knowledge of aBSR for each respective carrier, a network can either enable carrierswitching for UL transmissions, as described above, or indicate to theUE to suspend carrier switching for UL transmission with the possibleexception of PUCCH or SRS transmissions. UL switching can again beactivated after a UE reports a non-empty buffer for a particularcarrier. The above can be particularly applicable in case a secondarycell supports delay-tolerant services while delay-sensitive services aresupported in the primary cell.

Separate HARQ-ACK timing can be defined for the situation where the ULcarrier switching is perform less frequently than described above sothat a UE can provide to a secondary cell HARQ-ACK feedback in a singleUL subframe per frame (or less frequently than a frame) where theHARQ-ACK feedback is in response to PDSCH receptions in the secondarycell over multiple DL subframes.

In another embodiment, that can be beneficial to delay-sensitiveservices, UL switching is initiated by the UE. In order to avoid delaysassociated with higher layer signaling of a BSR or backhaul delaysassociated with inter-eNodeB information exchange, a UE can beconfigured to transmit a “switch indicator” in a PUCCH. The switchindicator conveys a 1-bit information where a positive value (such as abinary 0) indicates that to a primary cell that the UE has data totransmit in the secondary cell (and thus requests UL carrier switching,as described above, to be enabled) and a negative value (such as abinary 1) indicates that the UE has an empty buffer for UL data to thesecondary cell and request UL carrier switching to be disabled. ThePUCCH structure for the transmission of the switch indicator can be asfor PUCCH format 1a.

One or more embodiments provide for FDD and FDD joint operation withnon-ideal backhaul.

The embodiments described above can be extended to the case of FDD andFDD joint operation/carrier aggregation with non-ideal backhaul betweencarriers (inter-eNodeB CA).When an FDD cell (cell 1) is aggregated withanother FDD cell (cell 2), the UL frequency switching pattern of cell 2can complement that of cell 1. For example, if cell 1 is configured anUL frequency switching pattern defined by FDD UL-DL configuration 4 asin Table 6, the corresponding UL frequency switching pattern for cell 2can be D for subframe 0, 5, 6, 7, 8 and 9; D/S for subframe 1 and 4; D/Ufor subframe 2 and 3. For each FDD UL-DL configuration in Table 6, thereis a corresponding complementary FDD UL-DL configuration. This isillustrated in Table 16 (where the original FDD UL-DL configuration 6 inTable 6 has been removed since it is the same as configuration 0). Whena first FDD cell is configured with a first FDD UL-DL configuration, theUE can determine a second FDD UL-DL configuration of a second FDD cell;hence explicit signaling of the FDD UL-DL configuration for the secondFDD cell is not needed.

TABLE 16 FDD UL-DL configurations for FDD and FDD carrier aggregationwith non-ideal backhaul. FDD UL-DL TTI/subframe number Config 0 1 2 3 45 6 7 8 9 Comment 0 (Table 8) D/U D/S D D D D D D D D/S Complementary to7 1 D/U D/S D D D/S D/U D/S D D D/S Complementary to 8 2 D/U D/S D D/SD/U D/U D/S D D/S D/U Complementary to 9 3 D/U D/S D D D D/S D/U D/U D/UD/U Complementary to 10 4 D/U D/S D D D/S D/U D/U D/U D/U D/UComplementary to 11 5 D/U D/S D D/S D/U D/U D/U D/U D/U D/UComplementary to 12 6 D/U D/S D D D D D D D D/S Complementary to 7 7 [D][D/S] [D/U] [D/U] [D/U] [D/U] [D/U] [D/U] [D/U] [D/S] Complementary to 0and 6 8 [D] [D/S] [D/U] [D/U] [D/S] [D] [D/S] [D/U] [D/U] [D/S]Complementary to 1 9 [D] [D/S] [D/U] [D/S] [D] [D] [D/S] [D/U] [D/S] [D]Complementary to 2 10 [D] [D/S] [D/U] [D/U] [D/U] [D/S] [D] [D] [D] [D]Complementary to 3 11 [D] [D/S] [D/U] [D/U] [D/S] [D] [D] [D] [D] [D]Complementary to 4 12 [D] [D/S] [D/U] [D/S] [D] [D] [D] [D] [D] [D]Complementary to 5

It follows that the DL association set index table K_(FDD) also needs tobe expanded to include FDD UL-DL configurations 6-11 of Table 16.Further details are omitted here as they can be easily worked out usingthe embodiments described herein.

The embodiments described above can be applied to the case of carrieraggregation between two FDD cells.

Although the present disclosure has been described with an exemplaryembodiment, various changes and modifications may be suggested to oneskilled in the art. It is intended that the present disclosure encompasssuch changes and modifications as fall within the scope of the appendedclaims.

What is claimed is:
 1. A method for performing an uplink carrierswitching for a sounding reference signal (SRS) transmission by an userequipment (UE), the method comprising: receiving information associatedwith the uplink carrier switching; and transmitting a SRS based on theinformation associated with the uplink carrier switching.
 2. The methodof claim 1, wherein the information associated with the uplink carrierswitching is received in a downlink control information format.
 3. Themethod of claim 1, wherein the information associated with the uplinkcarrier switching is received in a radio resource control (RRC) message.4. The method of claim 1, further comprising: receiving a request fortransmission of an aperiodic SRS; and transmitting the aperiodic SRSbased on the received request.
 5. A method for supporting an uplinkcarrier switching, the method comprising: transmitting, to a userequipment (UE), information associated with the uplink carrierswitching; and suspending data transmission to the UE based on theinformation associated with the uplink carrier switching.
 6. The methodof claim 5, wherein the information associated with the uplink carrierswitching is transmitted in a downlink control information format. 7.The method of claim 5, wherein the information associated with theuplink carrier switching is received in a radio resource control (RRC)message.
 8. The method of claim 5, further comprising: transmitting, tothe UE, a request for transmission of an aperiodic SRS.
 9. A userequipment (UE) for performing an uplink carrier switching for a soundingreference signal (SRS), the UE comprising: a processor; and atransceiver operably coupled to the processor, wherein the transceiveris configured to: receive information associated with the uplink carrierswitching, and transmit the SRS based on the information associated withthe uplink carrier switching.
 10. The UE of claim 9, wherein theinformation associated with the uplink carrier switching is received ina downlink control information format.
 11. The UE of claim 9, whereinthe information associated with the uplink carrier switching is receivedin a radio resource control (RRC) message.
 12. The UE of claim 9,wherein the transceiver is further configured to: receive a request fortransmission of an aperiodic SRS; and transmit the aperiodic SRS basedon the received request.
 13. A base station for supporting an uplinkcarrier switching, the base station comprising: a transceiver configuredto transmit, to a user equipment (UE), information associated with theuplink carrier switching; and a processor operably coupled to thetransceiver, wherein the processor is configured to suspend datatransmission to the UE based on the information associated with theuplink carrier switching.
 14. The base station of claim 13, wherein theinformation associated with the uplink carrier switching is transmittedin a downlink control information format.
 15. The base station of claim13, wherein the information associated with the uplink carrier switchingis received in a radio resource control (RRC) message.
 16. The basestation of claim 13, wherein the transceiver is further configured totransmit, to the UE, a request for transmission of an aperiodic SRS.